So I just bought my 2005 Legacy GT last week and wasn't sure if the oil had been changed and wanted to be sure so I decided to change it. I tried searching this on here so I could make sure nothing was different from my other 2 Legacys(90 & 91) but couldn't find one. So I thought I would try and make a guide for those that have just newly acquired one of these fine automobiles or have never changed their own oil before. Also couldn't find torque values so that is here as well.

Oil filter
Crush washer for drain plug (Optional, if you don't use one and you know who you are be my guest. I always use one.)
4.8 Quarts of oil (whatever brand makes you happy, not getting into what brand so please don't start posting about this)
Ramps or Jack and Jackstands
17mm wrench
Torque wrench with 17mm socket (optional)
Funnel
Oil pan

Time required: dependent upon the individual; my time was around an hour and a half. I like to clean things

Step 2: Raising vehicle

Place the vehicle in gear/park and use the Ebrake. For extra assurance, chalk one of the rear wheels. Either jack vehicle and place it on stands or use ramps. Ramps will only work if you aren't too low. Please be careful and take your time with either option. The factory manual that comes with the car will show you where and how to jack the car with the supplied jack located under the trunk carpet. Easy spot is the front middle jack pad and placing the stands on the rear control plates.

Step 3: Removing lower cover

Now the oil change can be done by simply removing the clips for the engine oil filter service hole cover and then rotating it out of the way. I prefered to remove the whole cover so I can inspect the bottom of the engine and other components for corrosion, condition and security.

To remove the clips use a flat head and get underneath the head and using a twisting motion to unseat the clip. They can be a little tricky as they get dirt and such in them and make it hard to unclip. There are 3 in the front of the bumper, 1 on the rear of the cover and 1 on each side of the wheel well.
Here is how the small oil filter cover rotates (Yes I am aware it is burnt. It is from the aftermarket headers)
Here is the wheel well holes

Filter and plug location

Step 4: Filter and plug removal

CAUTION: If you just got home from work or a drive and completed the previous steps, let the car sit for atleast 20 minutes to cool. If you only started your car to place it on ramps as I did the car should be cool enough to continue. Use your best judgement pertaining to how hot the car might be. I don't need a McDonalds lawsuit because I didn't tell you the car would be hot from driving it (although I just did).

Now place your oil drain pan under the plug and then take your 17mm wrench or socket wrench and remove the drain plug in a loosening/counterclockwise direction. Once it has started to rotate I slowly back it out by hand until it starts to drain, this helps me to control the flow otherwise you may end up with oil all over the place. Yes I am aware of the Fumoto Valve and that will not be discussed in this thread.
AGAIN if you can't hold onto the plug because it is burning your fingers stop to let the car sit and cool down.
I do the same with the oil filter by rotating it in a loosening/counterclockwise direction until oil starts to drain from it. I do it for the same reason as the drain plug, to control flow and not make a mess.
Now after you have removed the plug and filter you can take some time and inspect the underside of the engine while the oil drains. As I just recently purchased the car I wanted to make sure I didn't have any surprises. This is the best time to check your drive shaft boots for tears or leaking sterring rack or where that oil smell might be coming from. This might seem like a no brainer but actually take the time to look you might be surprised.

Step 5: Cleaning contact surfaces

Make sure to wipe the the old oil and dirt from the contacting surfaces of the filter and plug. *Also make sure none of the old rubber gasket remains stuck to the contecting surface. It can be removed with a non-metalic scraper if necessary.

Step 6: Installing filter and oil drain plug

Now many may ask if it is necassary to replace the crush washer or gasket (as Subaru calls it). This is kind of like which oil should I use question. I never did on the other 2 Legacys and the Haynes manual doesn't even mention. However I will on this car as this is a very new car to me and I plan to do everything in my power to take care if it. Also as I pointed out the filter and gasket from Subaru cost next to nothing. *The gasket/crush washer SHOULD be Replaced EVERYTIME. Subaru was kind enough to label the filter so you don't forget what you're doing
Tried to take a close up of the gasket. I place the flat side on the plug end
Now if you look at the filter you purchased, it will have insturctions directly on it for how to install it. Make sure to do the first step and place a little oil on the rubber gasket to make it seal properly. This is on the filter and in the manual. Sweet no guessing. Tighten as per instruction (usually 3/4 turn after contact with seating surface).
For the drain plug you will hand thread it in as to insure it doesn't become cross threaded and tighten it good-n-tight, not strip the threads tight! If you have a torque wrench then set torque to 33 FT-LBS/44 NM depending where you're from or as otherwise indicated. If you have pruchased an aftermarket drain plug it might have a different value.
Clean up any remaining oil from these areas and remove oil drain pan from underneath vehicle.

Step 7: Filling her up

Using the funnel is a car's best friend as it won't get fresh oil everywhere. If you didn't buy one you can cut the top off of a plastic bottle and use that. (great for road side emergencies).

For this year and model it is required to place 4.8 Quarts of oil in. *The 4.8 Quarts includes oil and filter change. Your vehicle may have a different capacity. If you are not sure (you can check the manual also), the best thing would be to pour in 4 Quarts, wait a couple minutes check the stick and pour until it is at the F mark. Remember you can always add more, but pour too much and you will need to drain the extra oil.

Once you have filled the oil to the required level secure the cap and dipstick and you are almost done.

Step 8: Reinstall cover and clean up

You can reinstall the lower cover or leave it off, your choice. If you broke the clips you can use zip ties for a temporary fix so don't fret.
Double check that you removed all the tools from underneath the car and that there isn't a lake of oil under there. Close the hood and lower the car in the opposite manner that it was raised.
Job Complete

Used oil can be deposited at must auto parts stores for no additional charge

Recording is a good way to remember when, how many miles and with what your fluid was replaced with. Great for noting any unusual things to keep an eye on. Also great for if you decide to sell the car.
Here is an example